The present invention relates generally to dancers for assisting in the transportation of a web of material through an apparatus. More specifically, the present invention relates to a vertical dancer for a form, fill, seal packaging machine.
Form, fill, seal packaging machines are utilized to produce, from a web of flexible film, a flexible container for housing material to be dispensed. Form, fill, seal packaging machines are utilized to seal pharmaceuticals, dairy products, wine, food stuffs, cosmetics, nutritional products, and other products in flexible containers. A form, fill, seal packaging machine provides an apparatus for packaging these products in an expedient manner.
In one type of form, fill, seal packaging machine, a web of heat sealable film is fed from a roller to a former or mandrel that folds the film, for example, into a tubular shape. The film is folded longitudinally and heat sealed along abutting longitudinal edges. The film is then passed around a fill system that deposits the product to be packaged into the film. To create individual packages, the web of film must be sealed across its width. These "transverse seals" function as a seal that forms a pouch in the web of film for receiving the material to be packaged, and seal the filled end of a previously filled pouch. After the transverse seals are created, the web may then be severed to create an individual bag.
In some types of packaging arts, including, inter alia, pharmaceuticals, food products, nutritional products, and dairy products, it is desirable to create flexible containers that include means for accessing the containers (hereinafter "ports"). As used herein, the term "ports" includes, without limitation, valves, ports and closures, fitments, and other means for accessing the container. Ports provide a means for establishing fluid communication between the container and an outside environment. An example of a container having a port is the VIAFLEX flexible container for parenteral solutions manufactured by Baxter Healthcare Corporation of Deerfield, Ill.
As stated above, to fold the film, a former is utilized. The former provides means for folding, or aligning, opposite sides of a web of substantially flat film so that the film can be created into flexible containers. When creating flexible containers from a web of film in a form, fill, seal packaging machine, it is important that, among other things: 1) the port extends from a bottom end of the resultant flexible container; and 2) that the sides of the film that define the resultant container are properly aligned. To accomplish this, it is critical that the film when it is fed to the former is properly positioned.
In one type of packaging machine, the film is fed to the former from a series of rollers that include a dancer and a "quarter turn." In this packaging machine, the film is fed to a first roller around a vertical dancer, around a second and third roller to the quarter turn, and then to the former. The dancer affords the ability to have a film reserve and allows a constant flow of film even in a "stop and go" process, such as in a packaging machine. The quarter turn functions to modify the flow path of the film from a horizontal flow path to a vertical flow path.
However, a number of disadvantages are exhibited by this prior method. When a web of film, having a different width than a previously used web of film is utilized, for making different size flexible bags, the quarter turn and last roller must be moved horizontally to accommodate the different width of film. This is necessary to insure that the two edges of the film are substantially, if not exactly, vertical as they approach the former. If the edges of the film are not vertical, the web of film will not be properly aligned when it is sealed.
Although the above assembly allows the quarter turn and last roller to be moved to accommodate a different width of film, when the quarter turn and last roller are moved the amount of surface contact of the film on the dancer is thereby varied. In this regard, the dancer in this construction moves on a rotatable arm as the angle of the film is varied. This causes the torque on the film to change which can effect the precision and alignment of the film in the machine. This can cause irregular forming of the web of film or can cause the driving rollers, that pull the film through the packaging machine, to pull more or less than the exact bag length necessary to create the flexible containers. This results in the driving rollers not being properly indexed.
Because the web of film is pulled through the packaging machine with a force of approximately 1 g, it is desirable, if not necessary, that a constant torque be exerted by the dancer on the web of film. But, as the dancer, in this prior method, moves on the rotatable arm, the torque exerted by the dancer on the film is varied.
In certain packaging machines, ports are attached to the web of film prior to the forming of the web of film. If ports are attached to the web of film prior to the film being formed, additional considerations must be taken into account with respect to a roller assembly including a dancer. Due to the port, the dancer or rollers over which the film passes must now accommodate the port in such a way that they do not damage the web of film or port as the film, having the port, is fed thereover.